1. Field of the Invention
The present invention relates to an adhesive structure and a method for manufacturing the structure. In particular, the invention relates to an adhesive structure with anisotropic conductive films (ACFs) for use in a liquid crystal display (LCD), and a method for manufacturing the structure.
2. Descriptions of the Related Art
Liquid crystal displays (LCDs) have become increasingly popular because they are not only less power consumption and lower radiation, but also lightweight and portable. In manufacturing LCDs, the panel is first formed, followed by a module assembly process to produce the final product.
In the module assembly process, one of the main steps is to bond the integrated circuit (IC) and the flexible printed circuit (FPC) onto the outer lead bonding (OLB) area of the panel (or glass substrate), so as to electrically connect the electrodes or circuits which were previously formed on the panel.
The integrated circuits can be bonded onto the panel using the so-called “chip on glass (COG)” manufacturing process. In the COG process, the bumps of the integrated circuit are bonded onto the electrodes of the panel by metallic connection, such as welding. Nevertheless, although welding can result in high conductivity, it may damage the components due to the high temperature. Because manufacturing technologies have progressively advanced, the components have not only become progressively minimized, but the distances between the bumps of the integrated circuit or between the pins of the flexible printed circuit have also gradually decreased. Thus, the metallic connection will easily short the circuit in the manufacturing processes, resulting in lower yield.
Presently, an anisotropic conductive film (ACF) is used for electrically conducting and connecting the integrated circuits or the flexible printed circuits to the panel. The anisotropic conductive film mainly comprises conductive particles and an isolation adhesive material. Generally, the anisotropic conductive film is manufactured into a roll tap, and thus, a portion of which will be needed is appropriately cut. In practice, the cover film on the anisotropic conductive film must be removed first. Then, the anisotropic conductive film is attached onto the panel, where the base file on the other side of the anisotropic conductive film is removed subsequently. After precisely positioning the film, the integrated circuit or the flexible printed circuit is bonded with pressure at a specific temperature and period. Thus, the isolation adhesive material will solidify to provide perpendicular conduction, lateral isolation and adhesive connection.
The outer lead bonding area on the panel 10 of a conventional LCD is shown in FIG. 1. The outer lead bonding area comprises two regions, where the first anisotropic conductive film 11 and the second anisotropic conductive film 13 are attached onto the two regions, respectively, during the manufacturing processes. Then, the integrated circuit 15 and the flexible printed circuit 17 can be disposed onto the regions, respectively, for bonding with pressure. Because the integrated circuit 15 and the flexible printed circuit 17 are formed with different materials, different anisotropic conductive films should be adopted. Thus, different roll taps will be applied in the manufacturing processes. Accordingly, the integrated circuit 15 and the flexible printed circuit 17 can electrically conduct with the circuits or electrodes on the panel 10 through the first anisotropic conductive film 11 and the second anisotropic conductive film 13, respectively.
However, this conventional manufacturing process requires that the first anisotropic conductive film 11 and the second anisotropic conductive film 13 be attached onto the panel sequentially. In other words, requiring two attaching steps greatly complicates the manufacturing processes. Moreover, for the attaching precisions of the films between the integrated circuit 15 and the flexible printed circuit 17 and the regions, some space needs to be reserved to prevent improper connection or bonding damages. In particular, the distance D1 between the integrated circuit 15 and the flexible printed circuit 17 may range approximately from 0.45 mm to 0.5 mm.
Given the above concerns, the conventional manufacturing processes result in undesirable complications. In panel design, the outer lead bonding area tends to be minimized for enlarging the scale of the display area or minimizing the size of the final product. Thus, an improved adhesive structure for simultaneously attaching the anisotropic conductive films onto the panel of the LCD is needed.